Did either of those use executive orders to circimvent Congress and rewrite laws?
Yes.
Links?
You're asking for examples? Is that because you're a dumbass who doesn't know recent history, and has no business debating on this site?
OK - Bush used an EO to forbid Federal funding of stem cell research. That's clearly an issue (funding) that should originate in the House.
Why was that not illegal?
because the federal government looked at the manner in which most stem cells were gathered( by aborting fetuses produced for the sole purpose of harvesting stem cells) orginated and decided that the government was not going to have the legal authority to sanction abortion for research. Hence leaving it to the private sector to fund its own research...
Now, if there is another safer and non lethal manner to harvest brain stem cells, the government may do well to assist in funding that.